CN116759247A

CN116759247A - Electrical switching apparatus

Info

Publication number: CN116759247A
Application number: CN202310732905.7A
Authority: CN
Inventors: 张华�; 叶雪峰
Original assignee: Htdisplay Langfang Electronic Technology Co ltd
Current assignee: Htdisplay Langfang Electronic Technology Co ltd
Priority date: 2023-06-20
Filing date: 2023-06-20
Publication date: 2023-09-15

Abstract

The invention discloses an electrical switching apparatus, comprising: the fixed contact component comprises a first fixed contact component and a second fixed contact component, and the first fixed contact component and the second fixed contact component are electrically connected with two wiring terminals of the circuit system; a moving contact member including a first moving contact member and a second moving contact member, the relationship of the second moving contact member and the first moving contact member being configured to: the second moving contact part makes the first moving contact part electrically conductive by contacting with the first moving contact part, and makes the first moving contact part electrically disconnected by separating from the first moving contact part; and an actuating mechanism configured to move the second moving contact member and the first moving contact member in a state of contact synchronously toward the first stationary contact member, and to move the second moving contact member away from the first moving contact member toward the second stationary contact member and then into contact with the second stationary contact member after the first moving contact member contacts the first stationary contact member.

Description

Electrical switching apparatus

Technical Field

The invention relates to the technical field of electric technology, in particular to an electric switching device applied to a high-voltage circuit.

Background

As is well known, an electrical switch connected to a circuit system for controlling the on/off of the circuit system generally includes a fixed contact member connected to two terminals of the circuit system and a movable contact member that moves to contact with or separate from the fixed contact member, and after the movable contact member contacts with the fixed contact, the movable contact member makes the fixed contact member electrically conductive to thereby make the circuit system conductive, and after the movable contact member separates from the fixed contact member, the fixed contact is opened to thereby make the circuit system open.

However, when the above-described electric switch is applied to a high-voltage circuit system, the following problems occur:

at the closing moment of the electric switch, i.e. at the moment of contact between the moving contact part and the stationary contact part, an arc may occur between the moving contact part and the stationary contact part, which arc causes instantaneous hyperthermia, thereby damaging the contact surface of the stationary contact part and the moving contact part and the surface quality near the contact surface, e.g. frequent arc-action causes pits or spikes to occur on the contact surface, thereby affecting the subsequent contact quality of the two contact parts, thereby affecting the stability of the circuit system.

To improve the above-mentioned problems, there is provided an electric switch in the prior art, which provides two sets of static contact members arranged in front of and behind each other, wherein a moving contact member finally contacts a back side static contact member by moving past the front side static contact member, and contacts the static contact while the moving contact member passes the front side static contact member, and an arc is generated at the moment of contact between the moving contact member and the back side static contact member, i.e., discharge, thereby avoiding arc generation when the moving contact member contacts the back side static contact. Since no arc is generated when the rear stationary contact member contacts the movable contact member, the surface quality of the contact surface of the rear stationary contact member and the vicinity thereof is not deteriorated, but the movable contact member is damaged by the arc only when passing through the front stationary contact member, and the surface quality of the movable contact member is improved.

However, although the moving contact member is less affected by the arc due to the instantaneous passage of the front side stationary contact member, the moving contact member is not completely eradicated from the arc, and the degree of the effect of the arc on the surface quality of the moving contact member increases under the long-term and frequent operation of the electric switch, thereby affecting the contact quality of the moving contact member and the rear side stationary contact member, and thus affecting the stability of the circuit system. .

Disclosure of Invention

In view of the foregoing technical problems in the prior art, embodiments of the present invention provide an electrical switching apparatus.

In order to solve the technical problems, the technical scheme adopted by the embodiment of the invention is as follows:

an electrical switching apparatus comprising:

the fixed contact component comprises a first fixed contact component and a second fixed contact component, the first fixed contact component is positioned at the front side of the second fixed contact component, and the first fixed contact component and the second fixed contact component are electrically connected with two wiring terminals of the circuit system;

a moving contact member comprising a first moving contact member and a second moving contact member, the relationship of the second moving contact member to the first moving contact member being configured to: the second moving contact part makes the first moving contact part electrically conductive by contacting with the first moving contact part, and makes the first moving contact part electrically disconnected by separating from the first moving contact part;

and an actuating mechanism configured to move the second moving contact member and the first moving contact member toward the first stationary contact member in synchronization in a state of being in contact, and to move the second moving contact member and the first moving contact member apart from each other toward the second stationary contact member and then into contact with the second stationary contact member after the first moving contact member is in contact with the first stationary contact member.

Preferably, the electrical switching apparatus further comprises a cylindrical housing; a first fixed base and a second fixed base are fixed in the shell, and the first fixed base is positioned at the front side of the second fixed base; wherein:

the middle part of the first fixed base is provided with a central channel;

the first static contact component comprises two first static contact pieces which are symmetrically and mutually separated and fixed at the front end of the first fixed base;

the second static contact component comprises two second static contact pieces which are symmetrically and mutually separated and fixed at the front end of the second fixed base;

the actuating mechanism comprises a movable base, a differential rod, a first spring, a second spring and an actuator; the movable base is arranged in the shell in an axially movable way, the movable base is provided with a guide hole with a through axis, the differential rod penetrates through the guide hole, the first spring and the second spring are respectively used for pushing the movable base and the differential rod towards a direction far away from the first fixed contact component, the actuator is used for pushing the differential rod towards the direction of the first fixed contact component, and when the actuator is pressed, the first spring yields before the second spring;

the first movable contact component comprises two first movable contact pieces which are symmetrically and separately fixed on the movable base and correspond to the arrangement positions of the two second fixed contact pieces in the circumferential direction;

the second movable contact comprises a connecting arm and contact arms positioned at two sides of the connecting arm, the middle part of the connecting arm is fixed at the head part of the differential rod, and the two contact arms correspond to the gap between the two first movable contact pieces and the gap between the two second static contact pieces;

the actuator is used for pushing and driving the differential rod towards the direction of the fixed contact component.

Preferably, a plurality of first protruding strips which are circumferentially arranged are formed on the front end surface of the first fixed base, a plurality of strip-shaped through grooves which are circumferentially arranged are formed on the first static contact, and the plurality of first protruding strips correspondingly penetrate through the plurality of strip-shaped through grooves, so that the area between the strip-shaped through grooves is separated by the first protruding strips; the first movable contact piece is provided with a plurality of second raised strips which are circumferentially arranged, and the second raised strips correspondingly enter into areas among the first raised strips to be contacted with the first static contact piece.

Preferably, a radially extending separation strip is arranged on the front end surface of the second fixed base, and two second static contact pieces are arranged on two sides of the separation strip;

the contact arm of the second movable contact component comprises a U-shaped part positioned in the middle and side wings positioned at two sides of the U-shaped part; the width of the opening of the U-shaped part is larger than the span of the separation strip, and the flanks on two sides of the contact arm are used for being contacted with the two second static contact pieces.

Preferably, an inclined part and a secondary bending part are arranged between the connecting arm and each contact arm so that the contact arm can make elastic contact with the second static contact.

Preferably, a first step part is arranged on the inner hole wall of the shell, a second step part is arranged on the outer peripheral surface of the movable base, and the first spring is arranged between the first step part and the second step part; wherein:

the first fixed base is located at a rear side of the first stepped portion so that the first moving contact member contacts the first fixed contact member after the head portion of the differential lever passes through the first stepped portion.

Preferably, a third step part is arranged on the differential rod, a baffle ring is arranged in the guide hole, and the second spring is arranged between the third step part and the baffle ring.

Preferably, the electric switching device further comprises conductors arranged on two sides of the shell, the conductors comprise a converging portion and two branches connected with the inner ends of the converging portion, the two branches are respectively and electrically connected with the first static contact piece and the second static contact piece, and the outer ends of the converging portion extend out of the shell and are connected with the wiring terminals.

Preferably, the front end of the first fixing seat, the front end of the second fixing base, the head of the movable base and the head of the differential rod are all made of ceramic materials.

Compared with the prior art, the electric switch device disclosed by the invention has the beneficial effects that:

1. the electric switching device provided by the invention can effectively reduce or avoid the influence of electric arcs on a closed stable state.

2. The electric switching device provided by the invention can reduce the damage of electric arcs to contacts.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

An overview of various implementations or examples of the technology described in this disclosure is not a comprehensive disclosure of the full scope or all of the features of the technology disclosed.

Drawings

In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. The same reference numerals with letter suffixes or different letter suffixes may represent different instances of similar components. The accompanying drawings illustrate various embodiments by way of example in general and not by way of limitation, and together with the description and claims serve to explain the inventive embodiments. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Such embodiments are illustrative and not intended to be exhaustive or exclusive of the present apparatus or method.

Fig. 1 is a schematic perspective view of an electrical switching apparatus according to an embodiment of the present invention (a first moving contact member is in a state separated from a first fixed contact member).

Fig. 2 is a front cross-sectional view of an electrical switching apparatus (a first movable contact member is in a state of being separated from a first stationary contact member) according to an embodiment of the present invention.

Fig. 3 is a schematic perspective view of an electrical switching apparatus according to an embodiment of the present invention (a first moving contact member is in contact with a first stationary contact member).

Fig. 4 is a front cross-sectional view of an electrical switching apparatus (a first movable contact member is in contact with a first stationary contact member) according to an embodiment of the present invention.

Fig. 5 is a schematic perspective view of an electrical switching apparatus according to an embodiment of the present invention (a second moving contact member is in contact with a second stationary contact member).

Fig. 6 is a front cross-sectional view of an electrical switching apparatus (second movable contact member in a state of contact with second stationary contact member) according to an embodiment of the present invention.

Fig. 7 is a schematic perspective view of a connection state between a second moving contact member and a differential lever in an electrical switching apparatus according to an embodiment of the present invention.

Fig. 8 is a schematic perspective view illustrating an arrangement state of a first movable contact component and a first fixed base in an electrical switching apparatus according to an embodiment of the present invention.

Fig. 9 is a schematic perspective view illustrating an arrangement state of a second movable contact component and a second fixed base in an electrical switching apparatus according to an embodiment of the present invention.

Reference numerals:

11-a first stationary contact part; 111-a first stationary contact; 1111-strip-shaped through grooves; 12-a second stationary contact part; 121-a second stationary contact; 21-a first moving contact part; 211-a first movable contact; 2111-second ridge; 22-a second moving contact part; 221-contact arms; 2211-side wings; 2222-U-shaped portion; 222-connecting arms; 223-secondary bending part; 224-inclined portion; 31-a first fixed base; 311-first convex strips; 312-central passage; 32-a second fixed base; 321-dividing strips; 33-a movable base; 34-differential lever; 41-a first spring; 42-a second spring; 51-a first step; 52-a second step; 53-a third step; 54-baffle ring; 60-a housing; 61-a first end cap; 62-a second end cap; 70-conductor; 71-branch; 80-actuator.

Detailed Description

Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The terms "first," "second," and the like, as used herein, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof, but does not exclude other elements or items. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", etc. are used merely to indicate relative positional relationships, which may also be changed when the absolute position of the object to be described is changed.

In order to keep the following description of the embodiments of the present invention clear and concise, the detailed description of known functions and known components thereof have been omitted.

As shown in fig. 1 and 2, an embodiment of the present invention discloses an electrical switching apparatus including: the housing 60, the first fixed base 31, the second fixed base 32, the movable base 33, the first stationary contact member 11, the second stationary contact member 12, the first movable contact member 21, the second movable contact member 22, the first spring 41, the second spring 42, and the actuator 80.

The housing 60 is arranged in a substantially cylindrical structure, and both ends of the housing 60 are provided with a first end cover 61 and a second end cover 62, respectively, so that the electric switching device is arranged in a substantially closed configuration. The housing 60 may be made of a ceramic material or other insulating material.

The first fixing base 31 is fixed in the housing 60, the second fixing base 32 is fixed in the housing 60, and the first fixing base 31 is located in front of the second fixing base 32.

It should be noted that: the "front" direction and the "rear" direction are the directions in which the moving contact member is positioned closer to the moving contact member, referred to as the front direction, and the direction in which the moving contact member is positioned away from the moving contact member, referred to as the rear direction, respectively, and the "lower" direction corresponds to the "front" direction and the "upper" direction corresponds to the "rear" direction in fig. 2, respectively, as shown in fig. 2. In the following, the "lower" may be used instead of the "front" and the "upper" may be used instead of the "rear" in order to better facilitate the description of the structure of the device in connection with the figures.

The first fixing base 31 includes two fan-shaped structures symmetrically arranged to each other such that a central passage 312 allowing a solid part to pass therethrough is formed therebetween, and a lower portion or the whole of the first fixing base 31 is configured as an insulator.

The first stationary contact part 11 is fixed to the lower end surface of the first fixed base 31, specifically, the first stationary contact part 11 includes two first stationary contact pieces 111, the outer shapes of the two first stationary contact pieces 111 are approximately matched with the first fixed base 31, and the two first stationary contact pieces 111 are respectively fixed to the lower end surfaces of the two fan-shaped structures.

The second fixing base 32 has a ring-shaped structure, and a lower portion and an entire portion of the second fixing base 32 are configured as an insulator.

The second stationary contact part 12 is fixed to the lower end surface of the second fixing base 32, specifically, the second stationary contact part 12 includes two second stationary contacts 121, the two second stationary contacts 121 are substantially in a semi-circular shape, the two second stationary contacts 121 are symmetrically arranged, and a certain gap is maintained between the two second stationary contacts 121, and the arrangement direction of the two second stationary contacts 121 in the circumferential direction is consistent with the arrangement direction of the two first stationary contacts 111.

The two sides of the housing 60 in the radial direction are provided with conductors 70, respectively, each conductor 70 having a junction and two branches 71 formed at the inner ends of the junction, the two branches 71 of the two conductors 70 being connected with a first stationary contact 111 and a second stationary contact 121, respectively, the junction of the conductors 70 passing through the housing 60 for connection to terminals of a circuit system, thereby enabling the electrical switching apparatus to be connected into the circuit system.

The movable base 33 has a columnar structure, the movable base 33 is disposed in the housing 60 and located below the first fixed base 31, and can move axially along the housing 60, and the movable base 33 is provided with a guide hole that penetrates axially.

The first movable contact member 21 is fixed to the upper end surface of the movable base 33, and specifically, the first movable contact member 21 includes two first movable contacts 211, the two first movable contacts 211 are substantially semicircular, the two first movable contacts 211 are symmetrically arranged, a certain gap is maintained between the two first movable contacts 211, and the gap between the two first movable contacts is substantially equal to and axially opposite to the gap between the two second stationary contacts 121. As shown in fig. 3 and 4, the movable base 33 moves upward to bring the two first movable contacts 211 of the first movable contact member 21 into contact with the two first stationary contacts 111 of the first stationary contact member 11.

The differential lever 34 is inserted through the guide hole of the movable base 33, and the differential lever 34 is axially movable with respect to the movable base 33, so that the upper end of the differential lever 34 can protrude from the upper end of the movable base 33, and the lower end of the differential lever 34 always protrudes from the second end cover 62 of the housing 60.

The second moving contact member 22 is fixed at the upper end of the differential lever 34, the second moving contact member 22 is configured in a strip-shaped structure, and makes the second moving contact member 22 opposite to a gap between the two first moving contact pieces 211 of the first moving contact member 21 in a circumferential position, when the differential lever 34 is in a retracted state, the second moving contact member 22 just falls at the gap between the two first moving contact pieces 211 and contacts with edges of the two first moving contact pieces 211, thereby electrically conducting the two first moving contact pieces 211, and when the differential lever 34 is in an extended state, the second moving contact member 22 is separated from the two first moving contact pieces 211, so that the two first moving contact pieces 211 are electrically disconnected.

The first spring 41 is configured to push down against the movable base 33, specifically, a first step portion 51 is formed on an inner hole wall of the housing 60, a second step portion 52 located below the first step portion 51 and facing the first step portion 51 is disposed on the movable base 33, and the first spring 41 is disposed between the first step portion 51 and the second step portion 52, so that the first spring 41 applies a downward elastic force to the movable base 33, and the first movable contact component 21 and the first fixed contact component 11 are kept in a separated state in a natural state.

The second spring 42 is used for pushing down against the differential lever 34, specifically, an upward third step portion 53 is provided on the outer peripheral surface of the differential lever 34, a baffle ring 54 is mounted on the hole wall of the guide hole, the baffle ring 54 is located above the third step portion 53, the second spring 42 is provided between the baffle ring 54 and the third step portion 53, so that the second spring 42 applies downward elastic force to the differential lever 34, and the second moving contact member 22 and the first moving contact member 21 are kept in a contact state in a natural state.

In the present invention, the elastic coefficient of the first spring 41 is smaller than that of the second spring 42, so that the first spring 41 yields before the second spring 42 under the same urging force.

An actuator 80 is located below the differential lever 34 for pushing up against the differential lever 34, the actuator 80 may be an electric telescopic lever or an air cylinder.

The operation of the above-described electrical switch provided by the present invention is described below.

As shown in fig. 1 and 2, when the actuator 80 does not push the differential lever 34, the first spring 41 pushes the movable base 33 downward to separate the first movable contact member 21 from the first stationary contact member 11, and the second spring 42 pushes the differential lever 34 downward to keep the second movable contact member 22 in contact with the first movable contact member 21, at which time the electrical switching apparatus is in an off state.

When it is necessary to close the electrical switching apparatus, the actuator 80 is activated, so that the actuator 80 pushes up against the differential lever 34, and at the same time, the movable base 33 moves up with the differential lever 34 by means of the second spring 42, and since the elastic coefficient of the first spring 41 is smaller than that of the second spring 42, the first spring 41 is first yieldingly compressed, as shown in fig. 3 and 4, so that the first movable contact member 21 is brought into contact with the first stationary contact member 11, i.e., the two first movable contacts 211 are brought into contact with the two first stationary contacts 111, respectively, while the second movable contact member 22 is still kept in contact with the two first movable contacts 211. At this instant, both terminals of the circuitry are electrically conductive.

At the moment the first movable contact piece 211 is in contact with the first stationary contact piece 111, an arc may be generated between the first movable contact piece 211 and the first stationary contact piece 111, and the arc may damage the quality of the contact surface of the first movable contact piece 211 and the first stationary contact piece 111, however, since the second movable contact piece 22 is always kept in contact with the first movable contact piece 211 before the first movable contact piece 211 is in contact with the first stationary contact piece 111 and at the moment of contact, the arc is not generated between the second movable contact piece 22 and the first movable contact piece 211, and thus the second movable contact piece 22 is not damaged by the arc.

After the first moving contact part 21 contacts the first fixed contact part 11, the second spring 42 yields, the continuous movement of the differential lever 34 separates the second moving contact part 22 from the first moving contact part 21, so that the electric switching device is instantaneously opened to complete the discharge, the second moving contact part 22 continues to move toward the second fixed contact part 12, and then, as shown in fig. 5 and 6, the second moving contact part 22 moves to the gap between the two second fixed contacts 121 of the second fixed contact part 12 and contacts with the edges of the two second fixed contacts 121, so that the second moving contact part 22 is electrically conducted, and the two terminals of the circuit system are electrically conducted.

Since the second moving contact member 22 and the second stationary contact member 12 are not damaged by the arc during the entire closing process of the electrical switching apparatus, the electrical switching apparatus is stable in the electrically conductive state even if the electrical switching apparatus is used for a long period of time and frequently.

When the circuit system needs to be disconnected, the pushing force of the actuator 80 to the differential lever 34 is withdrawn, at this time, the first moving contact member 21 is separated from the first stationary contact member 11, the second moving contact member 22 is separated from the second moving contact member 22, and the second moving contact member 22 finally comes into contact with the first moving contact member 21 again under the action of the first spring 41 and the second spring 42.

In some preferred embodiments, as shown in fig. 3 and 8, a plurality of first protruding strips 311 are formed on the front end surface of the first fixing base 31, a plurality of strip-shaped through slots 1111 are formed on the first stationary contact 111, and the plurality of first protruding strips 311 correspondingly pass through the plurality of strip-shaped through slots 1111, such that the areas between the strip-shaped through slots 1111 are separated by the first protruding strips 311; the first movable contact 211 is formed with a plurality of second protrusions 2111 circumferentially arranged thereon.

At the moment when the first movable contact member 21 contacts the first stationary contact member 11, the plurality of second protrusions 2111 enter the areas between the plurality of first protrusions 311 to contact the first stationary contact 111, and thus, the arc only occurs in the areas between the two first protrusions 311, so that the arc can be effectively blocked, the arc is prevented from being connected into a sheet-like area, and the damage of the arc to the first movable contact 211 and the first stationary contact 111 can be effectively reduced.

In some preferred embodiments, as shown in fig. 5, 6, 7, and 9, a separation bar 321 extending in a radial direction is provided on the lower end surface of the second fixing base 32, so that two second stationary contacts 121 are arranged at both sides of the separation bar 321, that is, a gap between the two second stationary contacts 121 is filled with the separation bar 321, and the thickness of the second stationary contacts 121 is made smaller than the height of the separation bar 321, so that the two second stationary contacts 121 can be effectively prevented from being broken down by electric current. The second movable contact member 22 is configured to include a connection arm 222 and contact arms 221 integrally formed at both sides of the connection arm 222, and configures the contact arms 221 to a U-shaped portion 2222 at the center and side wings 2211 formed at both sides of the U-shaped portion 2222, and makes the width of the U-shaped portion 2222 larger than the width of the separation bar 321. When the second movable contact member 22 contacts the first movable contact member 21, the U-shaped portion 2222 is located in the space between the two first movable contact pieces 211, and the two side wings 2211 overlap the two first movable contact pieces 211, respectively, so that the second movable contact member 22 contacts the first movable contact member 21. The U-shaped portion 2222 is fastened outside the separation bar 321, and the two side wings 2211 overlap with the edges of the second stationary contact 121, so that the second movable contact member 22 contacts the second stationary contact member 12.

In some more preferred embodiments, as shown in fig. 7, an inclined portion 224 and a secondary bending portion 223 are disposed between the contact arm 221 and the connection arm 222 of the second moving contact member 22, so that when the second moving contact member 22 contacts the second fixed contact member 12, the inclined portion 224 and the secondary bending portion 223 can make the second fixed contact member 12 contact the second moving contact member 22 with a certain elastic pre-tightening force, so as to effectively avoid the problem of connection failure caused by axial play of the differential lever 34.

In some preferred implementations, as shown in fig. 6, the first fixed base 31 is disposed above the first step 51, so that the first moving contact member 21 makes contact with the first stationary contact member 11 only after the upper end of the differential lever 34 passes upward beyond the first step 51, and thus, the contact area of the first spring 41 with the two contact members is blocked by the differential lever 34, thereby avoiding the arc generated between the two contact members from affecting the first spring 41.

The first fixed base 31, the second fixed base 32, the movable base 33 and the differential rod 34 are all made of ceramic materials, so that the electric switch device has better insulation performance and high temperature resistance. The housing 60 may be formed by combining a nylon material and a ceramic material, that is, the inner side of the housing 60 is made of a ceramic material and the outer side of the housing 60 is made of a nylon material.

The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, the scope of which is defined by the claims. Various modifications and equivalent arrangements of this invention will occur to those skilled in the art, and are intended to be within the spirit and scope of the invention.

Claims

1. An electrical switching apparatus, comprising:

2. The electrical switching apparatus of claim 1 further comprising a cylindrical housing; a first fixed base and a second fixed base are fixed in the shell, and the first fixed base is positioned at the front side of the second fixed base; wherein:

the middle part of the first fixed base is provided with a central channel;

3. The electrical switching apparatus of claim 2 wherein a plurality of first ribs are formed on a front end surface of the first fixed base, a plurality of strip-shaped through grooves are formed on the first fixed contact piece, the plurality of first ribs correspondingly pass through the plurality of strip-shaped through grooves, so that regions between the strip-shaped through grooves are separated by the first ribs; the first movable contact piece is provided with a plurality of second raised strips which are circumferentially arranged, and the second raised strips correspondingly enter into areas among the first raised strips to be contacted with the first static contact piece.

4. The electrical switching apparatus of claim 2 wherein a radially extending separator strip is provided on a front face of said second stationary base, two of said second stationary contacts being disposed on either side of said separator strip;

5. An electrical switching apparatus as claimed in claim 2 wherein an inclined portion and a secondary bent portion are provided between the connecting arm and each of the contact arms to enable the contact arms to make resilient contact with the second stationary contact.

6. The electrical switching apparatus of claim 2 wherein the inner bore wall of the housing is provided with a first stepped portion, the outer peripheral surface of the movable base is provided with a second stepped portion, and the first spring is disposed between the first stepped portion and the second stepped portion; wherein:

7. The electrical switching apparatus of claim 2 wherein the differential lever is provided with a third stepped portion, the guide hole is provided with a stopper ring therein, and the second spring is disposed between the third stepped portion and the stopper ring.

8. The electrical switching apparatus of claim 2 further comprising conductors disposed on either side of said housing, said conductors including a junction and two legs connected to an inner end of said junction, said two legs being electrically connected to said first stationary contact and said second stationary contact, respectively, an outer end of said junction extending out of said housing to connect to said terminal.

9. The electrical switching apparatus of claim 2 wherein the front end of the first fixed seat, the front end of the second fixed seat, the head of the movable seat, and the head of the differential lever are each made of a ceramic material.